It is general that the gas pouring and charging step in the method of manufacturing the gas-charged electric switches is performed by utilizing a pressure reducing chamber. Here, the pressure reducing chamber is the one which renders a gas substitution to be performable by discharging the interior gas by means of a reduction of pressure and thereafter supplying an inert gas (or clean air), that is, conventionally, gas pouring and charging step is generally performed by accommodating the container which houses therein the electric switch and is sealed except gas substituting ports in the pressure reducing chamber and carrying out indirectly the gas substitution by means of the pressure reduction of the pressure reducing chamber and of the inert gas supply thereto. Next, in the conventional method, the container subjected to the gas substitution is temporarily sealed at the gas substituting ports, taken out of the pressure reducing chamber into the general atmosphere and tightly sealed at the gas substituting ports by such measure as heat adhesion or the like.
Therefore, according to such general method, the container has to be once carried into the pressure reducing chamber and to be again returned to the general atmosphere after performing the gas substitution so that certain difficulty is involved in incorporating the method in a part of an integrated continuous production line performed in the general atmosphere by means of a belt conveyer system, and further the method is rendered complicated since the sealing of gas substituting ports is made once temporarily in the pressure reducing chamber and thereafter finally in the general atmosphere. Since the gas substitution with respect to the container according to such general method is, further, indirectly performed as a result of the gas substitution made with respect to the entire pressure reducing chamber, it takes a considerable time for elevating the concentration of gas in the respective containers to a predetermined level and, further, since the gas fed into the pressure reducing chamber but not poured into the respective containers is originally unnecessary, there arise a remarkable want of economy specifically when an expensive gas is used.